Question: just replaced a contactor that has a 277v coil. Turns out control voltage in this particular system is 230v. Contactor does pull in. Should I leave the contactor in, or replace contactor, with one that has a 230v coil?

It's a son of a ***** to get to, that's why I really don't want to.:whistle::whistle:

02-14-2013, 01:55 PM

koolkahuna

It depends on what are the consequences when it fails.
If it's comfort cooling and people just get cranky, that's one thing but if it's a refrigeration system where product loss is a possibility then you want to man up and do it.

If the pickup voltage is borderline then any variance in supply power or circuit resistance could cause it to drop out or worse, start chattering, which can take out the compressor, burn up the electrics, scare the owner, etc.

Personally I would change it. Less guilt in the back of my mind adding to my daily stress. :D

02-14-2013, 02:26 PM

flangehead

Actually the contactor energizes a fan coil squirl cage blower for air curtain heat at front doors of commercial bldg. no big load on control circuit. Thanks for the feed back. Probably will change the contactor. Probably

02-14-2013, 02:35 PM

timebuilder

First, your priority should be to find out why there is a 277 volt coil in that contactor if the supply voltage that the unit receives is 230 volts. Check the label for the unit and see what the unit is designed to take. If the unit is designed for 277 volts and it's wired to a 230 volt feed this is a code violation.

02-14-2013, 02:41 PM

Chris_Worthington

Quote:

Originally Posted by timebuilder

First, your priority should be to find out why there is a 277 volt coil in that contactor if the supply voltage that the unit receives is 230 volts. Check the label for the unit and see what the unit is designed to take. If the unit is designed for 277 volts and it's wired to a 230 volt feed this is a code violation.

And yet we wonder why a higher voltage motor running on a lower voltage would burn up a contactor?

02-14-2013, 02:53 PM

timebuilder

I would be wondering how the unit was installed for the wrong voltage.....

02-14-2013, 02:53 PM

flangehead

Actually, 480 3 phase comes in to the unit and supplies the electric heaters on L1. L2. L3. Then they take one of the phases ( 277) and run it to a step down transformer and go to 230 to power blower fan and 230 also runs through the controls

02-14-2013, 04:41 PM

timebuilder

So they installed an actual neutral conductor with those three 480 phases, correct?

02-14-2013, 05:23 PM

jdblack

Quote:

Originally Posted by timebuilder

So they installed an actual neutral conductor with those three 480 phases, correct?

How else do you get 277?

Sent from my SCH-I510 using Tapatalk 2

02-14-2013, 06:38 PM

timebuilder

Quote:

Originally Posted by jdblack

How else do you get 277?

Sent from my SCH-I510 using Tapatalk 2

When you have a 480 volt secondary, your phase-to-phase voltage is 480, and your phase to neutral voltage is 277. The neutral point is the center of the Wye secondary.

So, to get 277, you usually wire your load from a phase leg to neutral.

I suppose you could have a single phase stepdown transformer that happens to have a 277 volt secondary winding, but I have not seen one. Of course, nearly anything is possible.

Could we see a schematic of the air curtain?

02-14-2013, 06:56 PM

flangehead

Yes I did see a white lone neutral wire headed back to the panel. No schematics, it's a 1976 Nesbit fan coil

02-14-2013, 07:05 PM

jdblack

Quote:

Originally Posted by timebuilder

When you have a 480 volt secondary, your phase-to-phase voltage is 480, and your phase to neutral voltage is 277. The neutral point is the center of the Wye secondary.

So, to get 277, you usually wire your load from a phase leg to neutral.

I suppose you could have a single phase stepdown transformer that happens to have a 277 volt secondary winding, but I have not seen one. Of course, nearly anything is possible.

Could we see a schematic of the air curtain?

I appreciate the response and i apologize that my smartelic sarcasm wasnt picked up. :rolleyes:

I was rhetorically asking how you would get 277 from a 480 system without a neutral.